Post-combustion CO2 capture by aqueous ammonia in an advanced IGCC fired with high-sulphur coal

Coal is indispensable to satisfy the world’s thirst for energy as innovative coal technologies are for climate protection. This paper focuses on the integrated gasification combined cycle (IGCC) technology, based on its potentially higher cycle efficiency than competitive pulverized-coal steam cycles. However, cycle efficiency alone is not enough for CO2 emission mitigation, as a more significant decrease in CO2 emissions can be reached with the implementation of carbon capture and storage (CCS). In particular, an advanced air-blown IGCC system is considered when gasifying a coal with high-sulphur content, which is really relevant for the coal market. The sulphur removed as H2S from the coal-derived gas before fuelling the combustion turbine is used in a wet sulphuric acid process to supply an agent useful to control ammonia slip in a post-combustion CO2 capture system based on ammonia scrubbing and designed for a reduced energy demand. Thus, reducing the energy impact of the CCS technology will reflect on higher power plant efficiency, related to a presumable lower cost of the generated electricity, as a high-sulphur coal is used as fuel input. In detail, a cooled ammonia-based process is more attractive than a more conventional chilled ammoniabased solution, with overall IGCC efficiency equal to 41.7% for 90% of CO2 avoided and specific primary energy consumption (SPECCA) for CO2 avoided as low as 2.3 MJ/kgCO2. Although IGCC efficiency increases if lower levels of CO2 capture are considered, as plausible, the calculation results show the SPECCA for CO2 avoided ranging from 80% to 90% is almost constant.